Process of and apparatus for the production of viscose solutions



Feb. 18, 1941. G. A. M. HEIM 2,232,326

PROCESS OF AND APPARATUSL%OR THE PRODUCTION OF VISCOSE SOLUTIONS Filed Oct. 12, 1938 Patented Feb. 18,1941

UNITED STATES PATENT OFFICE PROCESS OF AND APPARATUS FOR THE PRODUCTION OF VISCOSE SOLUTIONS corporation of Delaware Application October 12, 1938, Serial No. 234,668 In Germany October 30, 1937 5 Claims.

This invention relates to the manufacture of artificial products from solutions, which are characterized by the fact that the degree of aging or ripening to which they are subjected prior to the formation of the products therefrom, materially alter the properties of the products. More particularly, the invention is directed to a process of and an apparatus for the production of rayon and other fibers from a plurality of batches of spinning solutions, the spinning of which is controlled in accordance with the degree of ripeness thereof in such manner that the solution actually being spun is maintained at a substantially constant degree of ripeness even throughout long spinning periods. While the invention will be described in its application to the manufacture of rayon threads from viscose, the invention is equally applicable to the manufacture of artificial products from other types of spinning solutions, and indeed, the benefits thereof may be had in the manufacture of any chemical compounds to the extent to which similar problems are encountered.

In the manufacture of rayon according to the viscose process, cellulose sheets are first soaked in a solution of sodium hydroxide to form alkali cellulose, and the excess lye is removed therefrom by pressure. Thereupon the alkali cellulose sheets are subjected to a shredding operation to reduce them to crumbs, and after a short aging period the crumbs of alkali cellulose are treated in a sulfiding churn with carbon bisulfide. The product of this reaction of the alkali cellulose with carbon bisulfide is cellulose xanthate, which upon being dissolved in a weak caustic soda solution forms viscose. Rayon filaments are spun from the viscose solution as thus formed by extruding the viscose through the minute orifices of a spinneret into a coagulating bath.

Viscose is not ordinarily used in its green or unripened state for spinning purposes, inasmuch as it has been found that, if the solution is allowed to age somewhat before spinning, the quality and uniformity of the spun product will be greatly improved. It has also been found that the spinning of viscose solutions of different ages results in the production of yarns having different physical properties, and the particular age at which viscose will produce a yarn having the desired properties has been a matter of concern and has involved much experimentation. It is generally conceded that viscose should be allowed to ripen up to a certain point or degree hefore it is passed on to the spinning machine, and

that this degree of ripeness of the solution should be maintained substantially constant as the spinning operation progresses. Furthermore, green viscose normally contains impurities which tend to clog the minute orifices in the spinnerets through which the viscose is extruded. It is cus- I tomary to remove these impurities by repeated filtration of the viscose solution, and this is done as a part of the aging process, the solution being pumped through a series of aging tanks and filtered between each tank.

As stated above, viscose of different degrees of ripeness, when spun, will produce threads having different physical properties, and up until the present time slight variations of this nature in rayon spun from one and the same batch of viscoagulating bath of the spinning machine, and 20 is customarily stored in so-called spinning or feed tanks from which is drawn the supply of viscose required by the spinning machines. These feed tanks are of such a size that several hours are required for the spinning room to use the entire contents of a single tank. The result is that a batch of viscose in a feed tank, Which'at the time it is placed therein is at the proper degree of ripeness for spinning, undergoes additional ripening before it is all utilized by the spinning ma- 80 chines, whereby variations in uniformity occur in yarn spun fro-m a single batch of viscose. This is one of the serious obstacles that the rayon industry has encountered and for which up until the present time it has devised no satisfactory solution.

The present invention provides a process of and an apparatus for simply and effectively overcoming the difficulties referred to above and it contemplates generally the provision of a process 40 process of and apparatus for continuously sup- 5'0 plying a uniform spinning solution to meet the requirements of a spinning machine over prolonged periods of operation.

Another object of the invention is the provision of a process and means for delivering to a spinning machine a continuous supply of a spinning solution having a uniform degree of ripeness from a plurality of sources while the solutions at the respective sources progress from 5 a state of unripeness to a state of overripeness during the spinning thereof.

A further object of the invention is the production of a spinning solution formed of unripe and overripe viscose solutions which, upon delivery to the spinning machines, will yield a product having uniform physical characteristics.

Other objects and advantages of this' invention will be apparent from a study of the following detailed description, when considered in connection with the accompanyingdrawing, wherein:

Figure l is a diagrammatic representation of a spinning tank system formed in accordance with this invention, and

Figure 2 is a diagrammatic representation of a system of spinning tanks formed in accordance with a modification of this invention by means of which results may be had comparable to those obtained by the use of the system of Figure 1.

In referring specifically to Figure 1, which illustrates the preferred embodiment of the apparatus of this invention, similar spinning tanks designated as [0, II, l2, l3, l4, l5, I5 and I! are connected by means of pipes I8, I9, 22, 2|, 22, 23, 24 and 25 to a ring main 26. Connecting pipes I8, l9, 2%), 2|, 22, 23, 24' and 25 are each provided with respective stop valves 27, 28, 29, 3t), 3!, 32, 33 and 34.

Ring main 25 between the points of connection of adjacent pipes l8, l9, 2!], 2|, 22, 23, 24 and 25 35 is provided with respective stop valves 35, 35, 31, 38, 3'9, and 4!, and similar valves 42 and 43 are provided in the lower run of the ring main in opposite sides of a discharge pipe 44 which is connected into the main pipe. A branch pipe 45 provided with a valve 45 is connected into the ring pipe 26 at a point which is adjacent the end of the lower run and remote from the section of the ring pipe which is under the control of valves 42 and 43. This branch pipe 5 45. is connected to pipe 44 at a point 4'1 spaced from the ring main. A similar branch pipe 48 containing a stop valve 49 is connected to the main 25 at a point on the lower run which is at the opposite side of the portion of the run con- 50 trolled by valves 42 and 43. Branch pipe 48 is connected to discharge pipe 44 substantially at the same point at which branch pipe 45 is connected thereto. Discharge pipe 44, between ring pipe 26, and the point of connection of the branch 55.pipes 45' and 48, has a pump 5!) arranged therein. Pump 50 is adapted to be driven at a varying speed by means of a conoid drive 5! which includes a driven shaft 52, a cone pulley 53, a belt 54, a longitudinally reversed cone pulley and a driving shaft 55. Beyond the point of connection 41 discharge pipe 44 is provided with a homogenizer or mixing device 51. Discharge pipe 44 beyond the homogenizer is connected to the spinning machine, or machines (not shown).

In the operation of the system illustrated in Figure 1,,the spinnig tanks in, ll, 12, I3, l4, l5, l6, and I! have viscose supplied thereto from a series of aging tanks (not shown). The supply of viscose to spinning tank It! is received from the oldest batch of viscose in the last aging tank andzspinning tank I l receives its supply of viscose from the next succeeding aging tank. The viscose solution suppliedto spinning tank I0 has been ripened to the proper degree for spinning whereas theviscose solution supplied to'spinning tank II is younger or unripened. Thus the viscose in tank It while being at the correct degree of ripeness will constantly age while the viscose in tank II which is not sufficiently ripen-ed for direct spinning will constantly age and thereby approach and subsequently exceed the correct degree of ripeness.

At the beginning: of a spinning period, which for example, may consume a weak, tank ID for the reasons to be hereinafter discussed has only half as much viscose delivered thereto as does tank H and therefore in practice tank 40 is half filled while tank Ii is completely filled. When utilizing all of. the tanks H], H, [2, l3, [4, I5, l6 and IT, valves 2'? and 28 are maintained open while valves 22, til, it 32, 33 and 34 are closed. Valves 35, 43 and 49 are closed and valves 36, 31, 38, 39-, 42, 4|, 42 and 4% are open. The quantity of viscose to be withdrawn for utilization in the spinning machine is ordinarily controlled by two H factors. First, air pressure is exerted upon the viscose inthe respective spinning tanks to force the solutions therefrom and, second, the quantity of viscose required by the spinning machines is controlled by pumps (not shown), which are placed at each individual spinning point, these two forces acting upon each other to maintain a state of equilibrium. More specifically, when operations are stopped on one or more spinning 0 machines the viscose requirement decreases and the air pressure on the viscose tank is automatically reduced accordingly, and conversely when a spinning machine is again placed in operation the air pressure on the tank is increased to meet the added requirement of the spinning pumps. Therefore, at the beginning of an operation the entire supply of viscose used by the spinning machines will be drawn from the tank [3 through a portion of ring main 26 and open valve 42, through pipe 44, pump 50 and mixing apparatus 5'! directly to the spinning room. 'Pump 50 is operated by the conoid drive 5! in a manner to constantly decrease the quantity of viscose being withdrawn from tank It). As the quantity of viscose supplied bytank H) is decreased, the spin- 45 ning machine pumps will withdraw from tank I I, which is under air pressure, a constantly increasing quantity of viscose. The viscose withdrawn from tank passes through another portion of ring main 2% comprising open Valves 38; 50 31, 38, 39, 40 and 4|; andthrough branch pipe 45 and its valve 45, respectively, through the point of connection 41 beyond pumpEB thereby to balance the diminishing supply of viscose from the pump. l he two viscose solutions being de- 55 livered from tanks Hi and H are as aforesaid of dififerent degrees of maturity but they are passed through mixing apparatu 5? together where they are completely homogenized into a viscose solu tion of uniform ripeness before it is conducted 50 to the spinning machines.

The" speed of the pump 52 isso regulated that after the lapse of about'one-half the time during which the spinning room utilizes the'contents ofan entire spinning, tank the pump'supplies only 65 about one-half of the'viscose solution required by the. spinning machines. Therefore, when this point in the operation is reached, tanks "land I I are each utilized. to. supply one-half of the quantity. of the viscose solution required. At 70 this? stage of" the operation conoid. drive 5-! is shiftedfsothat pumpfifl Whichhasbe'en operated at' a constantly diminishing: speed i is then operated'. at a constantly. increasing: speed. At this same'time valve 42' and'46 are closedandvalves 43 and 49 are opened. Pump 59 immediately begins to draw viscose from tank II at a constantly increasing rate. The passage of theviscose from tank II is no longer directed through branch pipe but instead it passes through valve 49 and into pipe 44, through the pump 59, and the mixing apparatus 51 while the residual viscose requirements are then drawn by the pumps of the spinning machines directly from tank I9 at a decreasing rate. The Viscose from tank I9 is drawn through branch pipe 48 and valve 49 and is admitted to pipe 44 at point 41 whereupon it passes with the viscose from tank II into and through the mixing device for the purposes heretofore discussed. The decrease in the rate of feed of the viscose solution from tank I9 is in direct ratio to the speed at which the viscose is pumped from tank I I.

The constantly increasing supply of .viscose drawn by pump 59 from tank II reaches its maximum when the content of tank II is reduced by one-half and tank I9 has become empty. At this stage of the operation the entire spinning room requirements are supplied by tank II through the medium of pump 59. Valve 21 of tank I9 is now closed and the valve 29 of tank I2 is opened. Tank I2 has been filled with a viscose solution of a lesser degree of maturity than that contained in tank I I and the air pressure is placed upon the solution in the tank. As the operation continues valves 35, 42 and 46 are opened and valves 36, 43 and 49 are closed. The conoid drive is now shifted over and the pump 59 begins to draw the viscose solution from tank II at a constantly decreasing rate through the ring main and valves 35 and 42 and pipe 44 while the additional viscose requirements are drawn from tank I2 as a result of valves 37, 38, 39, 49, 4! and 46 being open. The solution from tank I2 is mixed with the solution from tank I I which is being drawn by pump 59 and the solutions are homogenized in the mixer 51 in the manner previously referred to.

When the contents of tanks II and I2 have reached the stages of the contents of tanks I9 and I I at the time that tank I2 was brought into the operation, valve 28 of tank II is closed and valve 99 of tank I8 is opened as well as valve 36 in the ring pipe 28, valve 31 is closed and the series of valves are set as at the beginning of the operation. The withdrawal of the-solutions from tanks I2 and I3 is then carried on in the manner previously described with respect to the new empty tanks I9 and I I and as tank I2 becomes empty the remainder of the tanks are brought successively into operation in the manner described in the operation of the other tanks. It will be clear from the above that the operation may be continued by the refilling of the empty tanks and the utilization thereof after the contents of each tank in the system has been uti lized. However, the last tank to be utilized in a,

complete spinning operation is supplied with viscose only to one-half of its capacity.

In the operation of the system here described, it will be seen that the portion of viscose solution supplied by means of pump is of a predetermined amount at any stage of the operation. However, as noted above, the demand by the spinning machine may vary somewhat from time to time. Under normal conditions of operation, wherein a large number of spinning machines are employed, the supply of viscose solution from the tank under air pressure will vary to compensate for any irregularities in the demand. However,

care should be exercised to avoid substantial unbalance of the process if a relatively large proportion of the spinning machines are stopped during the spinning operation. In such case, the system is preferably readjusted to the new conditions by modification of the speed range within which the pump 59 operates.

Themodified system illustrated in Figure 2 is provided with spinning tanks 58, 59, 69, 6|, 62, 63, 64 and 65 and these tanks through the medium of pipes 66, 61, 68, 69, I9, II, I2 and I3 which are provided respectively with valves I4, I5, I6, I7, 18, I9, 89 and BI are connected to ring main 82. Arranged in the ring main between adjacent connecting pipes are valves 83, 84, 85, 86, 81, 88 and 89. The upper run of ring main 82 is provided at its end with parallel branches 99, 9! and 92 and the lower run of the main ring is provided with a similar series of branches 93, 94 and 95. The branches 99, 9|, 92, 93, 94 and 95 have arranged therein valves 96, 91, 98, 99, I99 and I9I respectively. Discharge pipe I92 is connected into the ring main 82 at a point intermediate the two series of branches and a mixing apparatus or homogenizer I93 is provided in discharge pipe I92. Pipe I92 like pipe 44 of the system illustrated in Figure 1 is connected to the spinning machines (not shown).

In discussing the specific operation of the system illustrated in Figure 2 reference will be had to a typical example. Tank 58 is first half filled with properly ripened viscose which is suflicient to last for a period of approximately 6 hours and tank 59 is completely filled with a younger or unripened viscose. Tanks 58 and 59 are both placed under air pressure and valves 96, 91 and 98 are opened together with valve I4. The remainder of the valves are maintained closed and therefore the properly ripened viscose from spinningtank 58 at the beginning of the operation supplies the full requirements of the spinning machines, the viscose passing from tank 58 through pipe 66 and valve 14 and then through branch pipes 99, 9I and 92, to and through discharge pipe I92 and homogenizer I93 to the spinning machines. After the system has been in operation for approximately 45 minutes, valve I5 is opened and valves. 84, 85, 86, 81, 88, 89 and 99 are opened so that a small quantity of the unripened viscose from tank 59 will be supplied to the mixing apparatus wherein it is homogenized with a correspondingly reduced proportion of viscose which is being drawn from tank 58.

After the system has been in operation for approximately another 60 minutes, valve 98 is closed so that the flow of viscose from tank 59 will be increased as the flow of viscose from tank 58 is diminished. At the end of an additional 27 minutes, valve I99 is opened and valve 96 is reopened, At this stage of the operation valves 96, 91, 98, 99 and I99 are open and the flow of viscose from tank 58 is only slightly greater than the flow of the unripened viscose from tank 59. Upon the expiration of an additional 30 minutes, valve 96 is closed whereby the operation proceeds with two valves open in each of the series of branch pipes and therefore one-half of the spinning room requirements are supplied at this time from each of the tanks 58 and 59. As the operation is continued and after the expiration of an additional 36 minutes, valve I9I is opened and this will cause a slightly increased amount of viscose to flow from tank 59 as compared to that which is flowing from tank 58. Subsequently upon the lapse of 30 additional minutes, valves 91 and I9I are closed. This causes the flow of viscose from tank 58 to pass through but one branch pipe, whereas the viscose flowing from tank 59 is being delivered through two branch pipes. Thereafter upon the expiration of an additional 27 minute period, valve IOI is again opened whereupon at the expiration of 60 minutes, tank 58 will have become empty and all of the valves of branches 93, 94 and being open, the full requirements of the spinning room will then be drawn from tank 59. Tank 58 is now removed from the operation by the closing of valve 14 and tank Gil is brought into operation by placing the same under air pressure and opening valve I6. Valve 83 is now opened and valve 84 is closed as well as valves 99, loll, and lfll. Valves 96, 91 and at are opened and the operation of the system is repeated in connection with the supply of viscose from tanks 59 and 69, the same as has been described in connection with the supply of viscose from tanks 58 and 59. When the supply of viscose in tank 59 has been exhausted, valve 15 is closed and tank Glis brought into the operation by the closing and opening of appropriate valves and the system is continued to be operated as aforesaid. The system is continued to be operated by the utilization of the supply from each of the tanks and the tanks may be refilled as desired. It is desirable at the end of a complete spinning operation to fill the last tank only to one-half of its capacity.

With respect to the operation of the system of Figure 2 with reference to the withdrawal of viscose from tanks 58 and 59 as specifically set forth, the following table provides a summary thereof in tabular form:

TABLE Change in status of proportioning valves 96, 97,

98, 99, 100, 101 after lapse of time periods indicated during withdrawal of viscose from tanks 58 and 59 Time in minutes Tank 58 Tank 59 96, 97, 98 open..- 99, 100, 101 shut 99 opened 100 opened 101 opened 101 closed 101 opened 98 closed While the foregoing description sets forth my invention in its preferred embodiment with modification thereof, numerouschanges may be made in the construction and operation thereof without departing from the spirit of the invention. Therefore, it is desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

What I claim is:

1. An apparatus for continuously effecting the formation of a spinning solution of predetermined maturity for use in a prolonged spinning operation in the manufacture of artificial products, comprising a plurality of supply tanks, means for withdrawing from one of said tanks a decreasing quantity of spinning solution and for withdrawing from another of said tanks a correspondingly increasing quantity of spinning solution, said means including a changeable speed power driven pump, and a homogenizer for mixing the spinning solution so withdrawn.

2. An apparatus for continuously effecting the formation of a spinning solution of predetermined maturity for use in a prolonged spinning operation in the manufacture of artificial products, comprising a plurality of feed tanks, a productforming device, a pipe-line connecting said feed tanks and said productforming device, means for withdrawing from one of said tanks a constantly decreasing quantity of spinning solution and for withdrawing from another of said tanks a correspondingly increasing quantity of spinning solu tion, said means including a changeable speed power driven pump, and means for uniting said solutions prior to delivery to said product-forming device.

3. In a process of forming synthetic products from a cellulose xanthate solution, the steps of regulating the quality of said products by employing a solution of a predetermined degree of maturity which comprise constantly withdrawing solution from a source of supply of under mature solution, constantly withdrawing solution from a source of supply of over mature solution, homogeneously mixing the said solutions as a continuing operation, changing the amounts of said solutions so mixed as the said solutions become more aged to constantly increase the proportion of the said under mature solution so mixed, conducting said mixed solution to a product-forming device as it is formed and forming products from said mixed solution.

4. A process of maintaining constant the degree of maturity of a spinning solution for artii ficial products at the time of its extrusion from a product-forming device, comprising the steps of uniting as a continuing operation increasing proportions of a flowing premature spinning solution with correspondingly decreasing proportions of a flowing post-mature spinning solution in the path of flow of said solutions from sources of supply to said product-forming device, continuously conducting the united solution as it is formed to said product-forming device and continuously forming products therefrom.

5. A process of effecting the formation of a spinning solution of predetermined maturity for use in a prolonged spinning operation in the manufacture of artificial products, comprising the steps of uniting as a continuous operation, predetermined proportions of a. premature spinning solution with predetermined proportions of a post-mature spinning solution in the path of flow of said solutions from sources of supply to a product-forming device, forming products from the united solution and during the product-forming operation continuing the uniting of the solutions while decreasing the proportions of the post-mature spinning solutions and correspondingly increasing the proportions of the premature spinning solutions.

GUSTAV A. lVI. HEIM. 

